The present invention relates to a process and apparatus for extruding an expansible dough, particularly for yeast dough goods, crisp breads and puffed breakfast cereals.
The present invention provides an extruded rope composed of three separate materials, for example, an outer expanded crispy layer and two different non-dough filler materials. The fillers are substantially non-expanded and their location within the outer dough layer is adjustable.
U.S. Pat. Nos. 4,113,819, 4,266,920 and 4,416,910, all to Hayashi et al., describe apparatus and processes for manufacturing multi-layered dough materials comprising layers of dough and fat or oil, such as butter. These processes involve co-extrusion of dough and fat through a die having concentric annular orifices to form a hollow tube in which an inner layer of fat is surrounded by an outer layer of dough. In U.S. Pat. Nos. 4,413,819 and 4,416,910, this tube is then collapsed under its own weight onto a first conveyor, which passes it under a rolling assembly comprising a plurality of rolls which are themselves carried around an endless belt. At the end of the first conveyor, the rolled sheet passes downwardly to an oscillating chute, which oscillates parallel to the direction of motion of the first conveyor, and are formed into a pile, comprising multiple plies of the sheet, on a second conveyor, which conveys it under a second rolling assembly generally similar to the first one already described.
In the apparatus shown in U.S. Pat. Nos. 4,113,819 and 4,416,910, both orifices of the co-extrusion die are annular. The patents discuss the possibility of using a die having orifices of flattened or rectangular form, but state that, since the elevation angles of various portions of the inner faces of the nozzles are considerably different from each other because of the required changes in the cross-section of the channels used to feed material to the orifices of such a flattened die, such flattened or rectangular orifices are to be avoided because the discharge speed is different between the middle and end portions of the rectangular orifices. Such changes in discharge speed would result in non-uniformity of the thickness of the layers of fat and dough forming the co-extruded tube, and might result in distortion or rupture of the tube. Also, if in accordance with the teachings of these patents' annular dies producing a hollow cylindrical tube are used, and if this tube is to have the diameter desirable to produce a sheet of the desired width for high-speed production, the dies required are extremely large, cumbersome and expensive to form.
U.S. Pat. No. 3,572,259 to Hayashi discloses a process in which a cylinder of dough filled with a filler is co-extruded in the same manner as in U.S. Pat. No. 4,113,819, and the co-extruded cylinder is thereafter formed into double-layered spheres. A similar method, not restricted to the co-extrusion technique of U.S. Pat. No. 4,113,819, is disclosed in U.S. Pat. No. 3,351,026 to Hayashi.
Other types of devices for providing additional material to a co-extruded product, are discussed as follows.
Moreland, in U.S. Pat. No. 4,028,024 teaches manufacture of filled capsules using a co-extruder. The product formed by this co-extruder is a capsule having a medicament or edible substance encased in a casing formed of gelatin or dough. The capsule may be a single color or may have different colors on opposite sides of a single capsule. This two-colored capsule is formed in the extruder by using different colored materials in conduits 13,14 of the apparatus of FIG. 4. As seen in this figure, the core material enters through an orifice 61 surrounded by a body part 59 having inlet openings on opposite sides thereof. This permits entry of the two differently colored materials on opposite sides of the orifice 61, with a body part 69 causing merging of the inner and outer layers into a single co-extrudate body. While three conduits are provided, only two materials are taught, having a total of potentially three different colors.
In U.S. Pat. No. 3,314,381 to Fries et al., an apparatus is shown for filling baked products. The "co-extrudate" product formed is in fact an extruded material forming the interior and the exterior material portions of the final extrudate product. A second material is injected into the body of the first material during extrusion thereof by a spiral-shaped member having a plurality of orifices therein, to release a second material in a spiral-shaped pattern into the first material.
Extruders currently used for processing yeast dough, crisp breads and puffed breakfast cereals are known and generally comprise one or more feed hoppers which regulate the dry ingredients fed into a twin screw cooker/extruder where water is directly added to the dry ingredients by means of a metering pump.
U.S. Pat. No. 4,217,083 to Machuque discloses a complete baking-extrusion-expansion process as shown in FIG. 1, with the extrusion head being the novelty of the invention. The extrusion head has a horizontal slot from which dough is extruded onto two pivotable extension bars. Also, note straps 22 of FIG. 6.
The article entitled "EXTRUDED CRISP BREAD FAST MOVER IN EUROPE", published in the magazine Snack Food, Oct. 19, 1982, discusses a twin screw cooker-extruder in which dough is extruded horizontally and passed onto a gauge roll which feeds to the cutter.
Because texture and shape are highly important in the manufacturing of food, and particularly for dough products, it is particularly important to maintain rigid controls upon the final end product. Sporadic surging of dough or filler material from a die head and extreme expansion of dough result in final products which are non-uniform in thickness and shape and in degree of expansion.
When occluded gas escapes from the extruded dough, a cellular textured product results. The cellular texture disperses the light impinging on the final product causing a lighter color as compared to a surface which is non-cellular or in which the cellular formation is not uniform. Therefore, extruded baked doughs which do not possess a uniform cellular structure do not exhibit a consistent uniform color from side to side.